mirror of
https://github.com/hwchase17/langchain
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290 lines
10 KiB
Markdown
290 lines
10 KiB
Markdown
# Quickstart Guide
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This tutorial gives you a quick walkthrough about building an end-to-end language model application with LangChain.
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## Installation
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To get started, install LangChain with the following command:
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```bash
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pip install langchain
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```
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## Environment Setup
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Using LangChain will usually require integrations with one or more model providers, data stores, apis, etc.
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For this example, we will be using OpenAI's APIs, so we will first need to install their SDK:
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```bash
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pip install openai
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```
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We will then need to set the environment variable in the terminal.
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```bash
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export OPENAI_API_KEY="..."
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```
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Alternatively, you could do this from inside the Jupyter notebook (or Python script):
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```python
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import os
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os.environ["OPENAI_API_KEY"] = "..."
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```
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## Building a Language Model Application
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Now that we have installed LangChain and set up our environment, we can start building our language model application.
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LangChain provides many modules that can be used to build language model applications. Modules can be combined to create more complex applications, or be used individually for simple applications.
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`````{dropdown} LLMs: Get predictions from a language model
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The most basic building block of LangChain is calling an LLM on some input.
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Let's walk through a simple example of how to do this.
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For this purpose, let's pretend we are building a service that generates a company name based on what the company makes.
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In order to do this, we first need to import the LLM wrapper.
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```python
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from langchain.llms import OpenAI
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```
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We can then initialize the wrapper with any arguments.
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In this example, we probably want the outputs to be MORE random, so we'll initialize it with a HIGH temperature.
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```python
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llm = OpenAI(temperature=0.9)
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```
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We can now call it on some input!
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```python
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text = "What would be a good company name a company that makes colorful socks?"
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print(llm(text))
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```
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```pycon
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Feetful of Fun
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```
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For more details on how to use LLMs within LangChain, see the [LLM getting started guide](../modules/llms/getting_started.ipynb).
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`````
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`````{dropdown} Prompt Templates: Manage prompts for LLMs
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Calling an LLM is a great first step, but it's just the beginning.
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Normally when you use an LLM in an application, you are not sending user input directly to the LLM.
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Instead, you are probably taking user input and constructing a prompt, and then sending that to the LLM.
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For example, in the previous example, the text we passed in was hardcoded to ask for a name for a company that made colorful socks.
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In this imaginary service, what we would want to do is take only the user input describing what the company does, and then format the prompt with that information.
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This is easy to do with LangChain!
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First lets define the prompt template:
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```python
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from langchain.prompts import PromptTemplate
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prompt = PromptTemplate(
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input_variables=["product"],
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template="What is a good name for a company that makes {product}?",
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)
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```
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Let's now see how this works! We can call the `.format` method to format it.
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```python
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print(prompt.format(product="colorful socks"))
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```
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```pycon
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What is a good name for a company that makes colorful socks?
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```
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[For more details, check out the getting started guide for prompts.](../modules/prompts/getting_started.ipynb)
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`````
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`````{dropdown} Chains: Combine LLMs and prompts in multi-step workflows
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Up until now, we've worked with the PromptTemplate and LLM primitives by themselves. But of course, a real application is not just one primitive, but rather a combination of them.
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A chain in LangChain is made up of links, which can be either primitives like LLMs or other chains.
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The most core type of chain is an LLMChain, which consists of a PromptTemplate and an LLM.
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Extending the previous example, we can construct an LLMChain which takes user input, formats it with a PromptTemplate, and then passes the formatted response to an LLM.
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```python
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from langchain.prompts import PromptTemplate
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from langchain.llms import OpenAI
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llm = OpenAI(temperature=0.9)
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prompt = PromptTemplate(
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input_variables=["product"],
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template="What is a good name for a company that makes {product}?",
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)
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```
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We can now create a very simple chain that will take user input, format the prompt with it, and then send it to the LLM:
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```python
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from langchain.chains import LLMChain
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chain = LLMChain(llm=llm, prompt=prompt)
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```
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Now we can run that chain only specifying the product!
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```python
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chain.run("colorful socks")
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# -> '\n\nSocktastic!'
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```
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There we go! There's the first chain - an LLM Chain.
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This is one of the simpler types of chains, but understanding how it works will set you up well for working with more complex chains.
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[For more details, check out the getting started guide for chains.](../modules/chains/getting_started.ipynb)
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`````
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`````{dropdown} Agents: Dynamically call chains based on user input
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So far the chains we've looked at run in a predetermined order.
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Agents no longer do: they use an LLM to determine which actions to take and in what order. An action can either be using a tool and observing its output, or returning to the user.
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When used correctly agents can be extremely powerful. In this tutorial, we show you how to easily use agents through the simplest, highest level API.
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In order to load agents, you should understand the following concepts:
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- Tool: A function that performs a specific duty. This can be things like: Google Search, Database lookup, Python REPL, other chains. The interface for a tool is currently a function that is expected to have a string as an input, with a string as an output.
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- LLM: The language model powering the agent.
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- Agent: The agent to use. This should be a string that references a support agent class. Because this notebook focuses on the simplest, highest level API, this only covers using the standard supported agents. If you want to implement a custom agent, see the documentation for custom agents (coming soon).
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**Agents**: For a list of supported agents and their specifications, see [here](../modules/agents/agents.md).
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**Tools**: For a list of predefined tools and their specifications, see [here](../modules/agents/tools.md).
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For this example, you will also need to install the SerpAPI Python package.
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```bash
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pip install google-search-results
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```
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And set the appropriate environment variables.
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```python
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import os
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os.environ["SERPAPI_API_KEY"] = "..."
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```
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Now we can get started!
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```python
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from langchain.agents import load_tools
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from langchain.agents import initialize_agent
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from langchain.llms import OpenAI
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# First, let's load the language model we're going to use to control the agent.
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llm = OpenAI(temperature=0)
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# Next, let's load some tools to use. Note that the `llm-math` tool uses an LLM, so we need to pass that in.
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tools = load_tools(["serpapi", "llm-math"], llm=llm)
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# Finally, let's initialize an agent with the tools, the language model, and the type of agent we want to use.
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agent = initialize_agent(tools, llm, agent="zero-shot-react-description", verbose=True)
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# Now let's test it out!
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agent.run("Who is Olivia Wilde's boyfriend? What is his current age raised to the 0.23 power?")
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```
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```pycon
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Entering new AgentExecutor chain...
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I need to find out who Olivia Wilde's boyfriend is and then calculate his age raised to the 0.23 power.
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Action: Search
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Action Input: "Olivia Wilde boyfriend"
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Observation: Jason Sudeikis
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Thought: I need to find out Jason Sudeikis' age
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Action: Search
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Action Input: "Jason Sudeikis age"
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Observation: 47 years
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Thought: I need to calculate 47 raised to the 0.23 power
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Action: Calculator
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Action Input: 47^0.23
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Observation: Answer: 2.4242784855673896
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Thought: I now know the final answer
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Final Answer: Jason Sudeikis, Olivia Wilde's boyfriend, is 47 years old and his age raised to the 0.23 power is 2.4242784855673896.
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> Finished AgentExecutor chain.
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"Jason Sudeikis, Olivia Wilde's boyfriend, is 47 years old and his age raised to the 0.23 power is 2.4242784855673896."
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```
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`````
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`````{dropdown} Memory: Add state to chains and agents
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So far, all the chains and agents we've gone through have been stateless. But often, you may want a chain or agent to have some concept of "memory" so that it may remember information about its previous interactions. The clearest and simple example of this is when designing a chatbot - you want it to remember previous messages so it can use context from that to have a better conversation. This would be a type of "short-term memory". On the more complex side, you could imagine a chain/agent remembering key pieces of information over time - this would be a form of "long-term memory". For more concrete ideas on the latter, see this [awesome paper](https://memprompt.com/).
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LangChain provides several specially created chains just for this purpose. This notebook walks through using one of those chains (the `ConversationChain`) with two different types of memory.
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By default, the `ConversationChain` has a simple type of memory that remembers all previous inputs/outputs and adds them to the context that is passed. Let's take a look at using this chain (setting `verbose=True` so we can see the prompt).
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```python
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from langchain import OpenAI, ConversationChain
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llm = OpenAI(temperature=0)
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conversation = ConversationChain(llm=llm, verbose=True)
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conversation.predict(input="Hi there!")
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```
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```pycon
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> Entering new chain...
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Prompt after formatting:
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The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
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Current conversation:
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Human: Hi there!
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AI:
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> Finished chain.
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' Hello! How are you today?'
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```
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```python
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conversation.predict(input="I'm doing well! Just having a conversation with an AI.")
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```
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```pycon
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> Entering new chain...
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Prompt after formatting:
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The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
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Current conversation:
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Human: Hi there!
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AI: Hello! How are you today?
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Human: I'm doing well! Just having a conversation with an AI.
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AI:
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> Finished chain.
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" That's great! What would you like to talk about?"
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``` |